A micropayments method and apparatus to control spam using a centralized server architecture. The central server receives requests from senders who want to send emails, and determines if the sender has a micropayments account with an adequate balance. If so, an encrypted stemp is sent back to the sender...http://www.google.se/patents/US20050182735?utm_source=gb-gplus-sharePatent US20050182735 - Method and apparatus for implementing a micropayment system to control e-mail spam
